The Negative Effects of Pesticides on Children

Because their body mass is so much lower than adults', toxicity testing fails to adequately take into account the negative effects of pesticides on children.

Wheat ears

The agricultural chemicals carried on food represent a more significant level of toxicity to children, who have lower body mass than adults and whose growing tissues are at greater risk of sustaining damage from pesticide exposure.

Photo by Fotolia/felinda

Content Tools

The conventional agriculture industry claims that the pesticides, herbicides and insecticides it uses are safe when used as directed, but peer-reviewed evidence suggests otherwise. André Leu investigates these claims in The Myths of Safe Pesticides (Acres U.S.A., 2014), translating technical jargon into layman’s terms to break down the five most-repeated myths about pesticide safety. The following excerpt is from chapter 1, “Myth #1: Rigorously Tested.”

You can purchase this book from the MOTHER EARTH NEWS store: The Myths of Safe Pesticides.

The USPCP and many scientific researchers have expressed concern that the current toxicology testing methodologies are grossly inadequate for children.

The USPCP report stated, “They [children] are at special risk due to their smaller body mass and rapid physical development, both of which magnify their vulnerability to known or suspected carcinogens, including radiation.”

This is a critically important issue given that, according to the USPCP, “Approximately 40 chemicals classified by the International Agency for Research on Cancer (IARC) as known, probable, or possible human carcinogens, are used in EPA-registered pesticides now on the market.”

The main food regulator in Australia and New Zealand, Food Standards Australia and New Zealand (FSANZ), acknowledged that children had the highest levels of dietary exposure to pesticides when they published the 20th Australian Total Diet Survey due to their size and weight ratios in relation to the amount of residues they receive from food. “In general, the dietary exposure to pesticide residues was highest for the toddler age group. This is due to the high food consumption relative to body weight.” FSANZ, along with most regulators, are not concerned about this because pesticide residues in food are usually below the maximum residue limits. However the USPCP and other scientific researchers have pointed out that the current testing protocols are based on testing mature animals and ignore the specific physiological differences between mature animals and the fetus, newborns, and developing young, including humans.

According to the USPCP, “Chemicals typically are administered when laboratory animals are in their adolescence, a methodology that fails to assess the impact of in utero, childhood, and lifelong exposures.”

This is a critical issue as there is a large body of published science showing that the fetus and the newborn are continuously being exposed to numerous chemicals. The USPCP stated, “Some of these chemicals are found in maternal blood, placental tissue, and breast samples from pregnant women and mothers who recently gave birth. These findings indicate that chemical contaminants are being passed on to the next generation, both prenatally and during breastfeeding.”

The U.S. President’s Cancer Panel not only expressed concern on the level of these chemical contaminants, they also pointed out that this issue is being ignored by regulators due to the critical lack of knowledge and researchers. “Numerous environmental contaminants can cross the placental barrier; to a disturbing extent, babies are born ‘pre-polluted.’ Children also can be harmed by genetic or other damage resulting from environmental exposures sustained by the mother (and in some cases, the father). There is a critical lack of knowledge and appreciation of environmental threats to children’s health and a severe shortage of researchers and clinicians trained in children’s environmental health.”

Dr. Theo Colborn, one of the world’s acknowledged leading experts on endocrine-disrupting chemicals and coauthor of Our Stolen Future, published a peer-reviewed study in the scientific journal Environmental Health Perspectives that examined these issues. The study reviewed of many of the scientific papers and showed the widespread extent to which children and the unborn are exposed to numerous pesticides. Multiple pesticide residues have been found in semen, ovarian follicular fluid, amniotic fluid, maternal blood, placental and umbilical cord blood, breast milk, meconium of newborns, and in the urine of children. She writes, “It is fairly safe to say that every child conceived today in the Northern hemisphere is exposed to pesticides from conception throughout gestation and lactation regardless of where it is born.”

The information from these numerous scientific studies shows that current regulatory systems around the world have failed to protect unborn and growing children from exposure to a massive cocktail of toxic pesticides. This has many serious implications especially the increase in a range of serious health issues in children and as adults later in life.

Pesticide Exposure Is Linked to Childhood Cancer

A number of studies show the link between chemical exposure, particularly exposure to pesticides, and the increase of cancer in children. The USPCP report states, “Cancer incidence in U.S. children under 20 years of age has increased....Leukemia rates are consistently elevated among children who grow up on farms, among children whose parents used pesticides in the home or garden, and among children of pesticide applicators.”

Pesticide Exposure Can Lead to Nervous System Damage

Many pesticides work as nerve poisons. These include organophosphates, synthetic pyrethroids, neonicotinoids, and carbamates. Organophosphates were first developed by German chemists in the 1930s looking to use them as pesticides. They were further developed by the Nazis as nerve gases for warfare in World War II, although it is doubtful they were ever used then. One of the best known organophosphate nerve gases is sarin, which was used to kill thirteen people in the Tokyo subway attack by the Aum Shinrikyo religious sect on March 20, 1995, and injure nearly a thousand. Saddam Hussein used a range of organophosphate nerve gases such as sarin and VX gas during the Iran-Iraq War to kill Iranian soldiers and on his own citizens, killing thousands of Kurds. The United Nations (UN) has stated that sarin gas was used by the Syrian government in the Damascus suburb of Ghouta in August 2013, killing an estimated 281 to 1,729 rebel fighters and civilians. The production and stockpiling of chemical weapons, including sarin, was banned in 1993 by the UN Chemical Weapons Convention. Organophosphates started to become a major class of pesticides after World War II with the commercialization of numerous types such as malathion, parathion, diazinon, chlorpyrifos, azamethiphos, dichlorvos, phosmet, fenitrothion, fenthion, dimethoate, omethoate, tetrachlorvinphos, etc.

Organophosphates react with and destroy a key nervous system enzyme called acetylcholinesterase. This enzyme is responsible for degrading acetylcholine, one of the neurotransmitter chemicals that fire nerve signals like bullets fired from a gun. Acetylcholine is found mostly in the muscle nerves and in the brain. Without acetylcholinesterase to “turn off ” acetylcholine, the nerves continue to fire signals, causing a range of symptoms such as intense headaches, nausea, vomiting, muscular paralysis, convulsions, and bronchial constriction. High levels of exposure can cause death from asphyxiation. Low levels of exposure are usually associated with “flu-like” symptoms—headaches, low energy, depression, and a general feeling of being unwell.

Standard toxicology usually regards the reactive degradation of acetylcholinesterase as the only way organophosphates poison animals and posits that they do not damage other metabolic pathways or body organs. Acetylcholinesterase levels will generally recover after low-level exposures, so it is assumed that no permanent damage results from such contact.

There are studies showing that organophosphate pesticides damage other tissues, including the myelin (the protective covering of nerve cells), and key nerves such as the optic nerve, causing permanent damage to eyesight including blindness. Other studies show genetic damage to the cell chromosomes. This is usually regarded as a sign of a precancerous condition.

Dr. Colburn reviewed numerous published papers on one of the most common organophosphates, chlorpyrifos (CPF). These papers detailed an amazing litany of diverse mechanisms in the way CPF affected many tissues and the nervous system, raising serious questions about the safety of CPF, other organophosphates, and all pesticides. These effects included damage to several areas of the brain and disruption of the development of the nervous system in the fetus and newborn that resulted in a range of behavioral problems later in life. She states “Most astounding is the fact that a large part of CPF’s toxicity is not the result of cholinesterase inhibition, but of other newly discovered mechanisms that alter the development and function of a number of regions of the brain and CNS [central nervous system].”

Developmental Neurotoxicity

Scientific research shows that many pesticides affect the normal development of the nervous system in fetuses and children. The brain is the largest collection of nerve cells, and there are several scientific studies showing that when the fetus and the newborn are exposed to minute amounts of these pesticides, even below the current limits set by regulatory authorities, brain function can be significantly altered.

Qiao et al. of the Department of Pharmacology and Cancer Biology at the Duke University Medical Center found that the developing fetus and the newborn are particularly vulnerable to pesticides in amounts lower than the levels currently permitted by most regulatory authorities around the world. Their studies showed that the fetus and the newborn possess lower concentrations of the protective serum proteins than adults. A major consequence is developmental neurotoxicity, in which the poison damages the developing nervous system. The scientists stated, “These results indicate that chlorpyrifos and other organophosphates such as diazinon have immediate, direct effects on neural cell replication....In light of the protective effect of serum proteins, the fact that the fetus and newborn possess lower concentrations of these proteins suggests that greater neurotoxic effects may occur at blood levels of chlorpyrifos that are nontoxic to adults. Contact with chemicals at levels below the regulatory limits can thus harm the fetus and breastfeeding children even if the mother shows no side effects from the contact.

One of the most concerning studies on this matter was published in 1998 by Guillette et al. in the peer-reviewed scientific journal Environmental Health Perspectives. The researchers compared the drawing abilities of four- and five-year-old Yaqui children in the Sonora region of Mexico. The study compared two groups of children that shared similar diets, genetic backgrounds, and cultural backgrounds. One group lived in the valley and was exposed to the drift of pesticides from the surrounding farms, and the other lived in the foothills where they were not so exposed. Both groups of children were asked to draw pictures of people. The children from the foothills drew pictures consistent with children their age. The children exposed to pesticides could not draw an image or could barely draw an image that represented a person. Most of their drawings resembled the scribbles of much younger children, indicating that pesticide exposure had severely compromised the development of their brain functions.

Brain Development Is Affected by Pesticide Exposure

Concerns raised by Guillette’s study about the development of brain function were validated by four later studies that showed that prenatal exposure to organophosphate insecticides (OPs) adversely affects the neurological development of children. The studies were conducted by researchers at the Columbia University Center for Children’s Environmental Health, the University of California, Berkeley, and the Mount Sinai School of Medicine. Each study was conducted independently, but they all came up with very similar results: fetal exposure to small amounts of OPs will reduce the IQ of children.  A study of farm worker families in California has shown that by age three and a half, children born to mothers exposed to OP insecticides have lessened attention spans and are more vulnerable to attention deficit hyperactivity disorder (ADHD). Male children were more likely to be impacted. According the Center for Disease Control and Prevention, Atlanta, Georgia, “The average annual increase in the percentage of children with all diagnoses of ADHD (with and without LD [learning difficulties]) was 3% from 1997 through 2006. No significant average annual change was found in the percentage of children with all diagnoses of LD (with and without ADHD).” While the overall trend for all types of learning difficulties is stable, the trend for ADHD is steadily increasing.

Parents should have considerable concern that the Columbia University study found no evidence of a lower-limit threshold of exposure to organophosphates in the observed adverse impact on intelligence. This means that even very low levels of exposure could lead to reductions in a child’s intelligence.

The study by Rauh et al., published in the journal Proceedings of the National Academy of Sciences of the United States of America, has confirmed the findings of the previous studies and shown a large range of brain abnormalities present in children exposed to chlorpyrifos in utero through normal, nonoccupational uses. Exposure to CPF in the womb, even at normal levels, resulted in “significant abnormalities in morphological measures of the cerebral surface associated with higher prenatal CPF exposure” in a sample of forty children between five and eleven years old.

The researchers stated that the current regulatory safety limits and testing methodologies are inadequate for determining safe exposure levels for children.

“Current safety limits are set according to levels needed to achieve inhibition of plasma cholinesterase, a surrogate for inhibition of acetylcholinesterase in the brain, long assumed to be the common mechanism by which organophosphates induce neurodevelopmental deficits. However, pathogenic mechanisms other than cholinesterase inhibition are almost certainly contributing to the deleterious effects of early exposure to organophosphates (21, 37), including the observed brain abnormalities and their accompanying cognitive deficits.”

Measuring the levels of cholinesterase in blood is the accepted method used to establish the level of exposure to organophosphates. If the levels are considered “normal” then it is assumed that there is no damage to the developing nervous system and the brain. The researchers state that the current assumption that the degradation of acetylcholinesterase is the only way that organophosphates affect the nervous system is incorrect. The abnormalities that the researchers found in the developing brains of children along with the cognitive deficits show that organophosphates have other mechanisms that cause damage.

The researchers recommended that the current limits set by regulatory authorities be revised based on these data. “Human exposure limits based on the detection of cholinesterase inhibition may therefore be insufficient to protect brain development in exposed children.”

The United States had banned all uses of chlorpyrifos on food and restricted it to non-food uses prior to these studies. Despite this effort, the exposure levels continue to cause neurodevelopmental problems in U.S. children. The U.S. EPA is now reviewing all uses of chlorpyrifos.

This study has even greater implications for the many countries that allow the use of chlorpyrifos in food crops, especially in the horticulture sector. It is one of the pesticides that are regularly detected in residue surveys of food. Children of these countries almost certainly have had a higher level of exposure to chlorpyrifos.

Another study published in Environmental Health Perspectives looked at a range of chemicals, including organophosphate pesticides, that were implicated in lowering the IQs of zero- to five-year-old U.S. children. It found that the reduction in IQ was substantial. The study concluded that “when population impact is considered, the contributions of chemicals to FSIQ [full-scale IQ points] loss in children are substantial, in some cases exceeding those of other recognized risk factors for neurodevelopmental impairment in children. The primary reason for this is the relative ubiquity of exposure.”

In a study published in the medical journal The Lancet Neurology, scientists from the University of Southern Denmark, the Harvard School of Public Health in Boston, and the Icahn School of Medicine at Mount Sinai, New York, expressed concern that the majority of commercially used chemicals, including pesticides, have not been tested for developmental neurotoxicity. The researchers noted that neurodevelopmental disabilities, including autism, attention-deficit hyperactivity disorder, dyslexia, and other cognitive impairments, affected millions of children worldwide. They stated, “To control the pandemic of developmental neurotoxicity, we propose a global prevention strategy. Untested chemicals should not be presumed to be safe to brain development, and chemicals in existing use and all new chemicals must therefore be tested for developmental neurotoxicity.”

A large body of published, peer-reviewed scientific research shows that pesticide exposure in children is linked to:

• Lower IQs
• Autism spectrum disorders
• Lack of physical coordination
• Loss of temper/anger management issues
• Bipolar/schizophrenia spectrum of illnesses
• Depression

The previous studies show that the current methods of determining the MRLs and ADIs for organophosphate and other pesticides are clearly out of date and need to be immediately revised based on the warnings of current, peer-reviewed science. There is an urgent need to investigate the many other biochemical pathways other than acetylcholinesterase that organophosphate and other neurotoxic pesticides can affect.

Negative Effects of Pesticides Can Be Heritable

Some of the most concerning studies show that pesticide damage can be passed on to the next generation. Not only are the offspring born with damage to the nervous system, the reproductive system, and other organs, the great-grandchildren can be as well.

Researchers in a 2012 study found that pregnant rats and mice exposed to the fungicide vinclozolin during the period when the fetus was developing reproductive organs developed genetic changes in the genes that were passed onto future generations. The researchers stated, “Transient exposure of the F0 generation gestating female during gonadal sex determination promoted transgenerational adult onset disease in F3 generation male and female mice, including spermatogenic cell defects, testicular abnormalities, prostate abnormalities, kidney abnormalities and polycystic ovarian disease. Pathology analysis demonstrated 75% of the vinclozolin lineage animals developed disease with 34% having two or more different disease states.”

Another study showed that when pregnant rats were exposed to a combination of permethrin, a common insecticide, and DEET (N,N-diethyl-meta-toluamide), the most common insect repellent, significant damage occurred in subsequent generations, including the great-grandchildren. The researchers found that “Gestating F0 generation female rats were exposed during fetal gonadal sex determination and the incidence of disease evaluated in F1 and F3 generations. There were significant increases in the incidence of total diseases in animals from pesticide lineage F1 and F3 generation animals. Pubertal abnormalities, testis disease, and ovarian disease (primordial follicle loss and polycystic ovarian disease) were increased in F3 generation animals.”

The significant issue with these two studies is that small exposures to pesticides at critical times in the development of the fetus can cause multiple diseases that are passed on to future generations. It means that pregnant women eating food with minute levels of pesticides could be inadvertently exposing their children, grandchildren and great-grandchildren to permanent damage to their reproductive systems and other organs.

The scientists found that 363 genes had been altered by the pesticides: “Analysis of the pesticide lineage F3 generation sperm epigenome identified 363 differential DNA methylation regions (DMR) termed epimutations [changes to the genes caused by environmental factors—in this case by pesticides]. Observations demonstrate that a pesticide mixture (permethrin and DEET) can promote epigenetic transgenerational inheritance of adult onset disease and potential sperm epigenetic biomarkers for ancestral environmental exposures.”

Genes play a major role in the development of hormone, metabolic, reproductive, nervous, and other body systems, and in the development of organs, limbs, the brain, and other body parts. When genes are altered, this means that the development of the systems and organs that are dependent on the genes are altered, leading to a range of diseases and other problems later in life.

This study is particularly distressing because DEET is the most common repellent used for mosquitoes and other insects. It is widely used on children and pregnant women.

The Negative Effects of Pesticides on Children Are Significant

The body of published, peer-reviewed science showing the wide range of problems caused by pesticides to the fetus and newborn is substantial and compelling. The current testing methodologies use adolescent through to adult animals. This means that they will not detect the adverse health issues that are specific to the unborn and small children.

Despite the fact that many professional experts in this area such as the USPCP, the WHO, and UNEP have been calling for specific toxicological studies that are relevant to the fetus and growing children to determine if the current MRLs and ADIs of pesticides are safe for them, regulatory authorities largely continue to ignore this dangerous oversight. Until these specific tests are done, regulatory authorities are using data-free assumptions that the current pesticides used in food, households, playgrounds, schools, and in the general environment are safe for our unborn and growing children. Regulation should not be based on assumptions but should use independently published, peer-reviewed scientific evidence to prove whether these toxins are safe. Given that our children are our future and most of them are exposed to multiple chemicals, time will prove the regulatory committees’ unwillingness to act against pesticides more serious than their decades of inaction over asbestos.

More from The Myths of Safe Pesticides:

Chemical Cocktails on Our Food

Reprinted from The Myths of Safe Pesticides by André Leu and published by Acres U.S.A., 2014. Buy this book from our store: The Myths of Safe Pesticides.